Maternal consumption of Great Lakes fish high in polychlorinated biphenyls (PCBs) or marine mammals high in both PCBs and methyl mercury (MeHg) has been associated with cognitive deficits in children. Recent evidence suggests that PCBs and MeHg may be acting in an additive or interactive fashion to produce some of these deficits. The overall goal of the proposed research is to evaluate neuropsychological and auditory outcomes in Asian American children potentially exposed perinatally to high levels of PCBs and MeHg through maternal consumption of fish from the highly polluted Fox River in Green Bay, WI. Building upon earlier efforts, a cohort of Hmong (n=535) and Laotian women (n=135) of reproductive age who reside in Green Bay or Appleton, Wisconsin, will be established to examine these relationships. An intervention program to reduce consumption of contaminated fish in this population will also be implemented and evaluated. At enrollment, two questionnaires are administered during an in-home interview: the first details demographic and lifestyle characteristics, and medical and reproductive history; and a fish consumption questionnaire. All women who agree to participate in the health effects phase of the study will be contacted monthly by telephone to determine if she has become pregnant and is therefore eligible (less than 16 weeks gestation) for this phase. Blood samples will be obtained at 20 and 28 weeks gestation, and again at delivery of the infant and 6 weeks postpartum; a cord blood sample will also be obtained. The toxicokinetics of PCBs during pregnancy will be examined by determining serum level changes at these various gestational stages, while considering potential important covariates including weight and hormonal fluctuations experienced as pregnancy progresses, as well as fish consumption during pregnancy. Fluctuations in MeHg as pregnancy progresses, as well as perturbations in thyroid hormone status in relation to PCB exposure, will be examined. The focus will be on specific aspects of cognitive, motor and sensory function that are affected by PCBs and/or MeHg in animal models, but have not been adequately assessed in human infants or children. These include auditory function, frontal lobe functions such as working memory, planning and response inhibition, and cerebellar functions such as balance and coordination. Information from the in-depth neurobehavioral assessments of PCB and MeHg exposed rats to be conducted in Project 3 will guide the selection of additional domain-specific tests that would be relevant in human children.